The present invention relates generally to video tape recorder, and more particularly to an auto tracking apparatus for automatically controlling tracking by utilizing the head switching pulse and the envelope waveform of the composite video signal detected by a reproducing head.
Various auto tracking apparatus have recently been put to practical use in the field of video tape recorders in order that a magnetic head can accurately scan a video signal-recorded track during reproduction, particularly, speed-varying reproduction such as slow-motion reproduction.
An example of a conventional auto tracking apparatus is disclosed in U.S. Pat. No. 4,451,860 or Japanese Patent Provisional publication No. 57-66526. These patents teach sampling and holding the detection output of a reproduction high frequency signal at a given point in a field and controlling the head position to keep the level of the detection output at a maximum.
However, such prior art apparatus encounter difficulty ensuring effective tracking control where the following of the track is not parallel to the center line thereof, because the sampling of the detection output signal is performed at only one point for each of plurality of fields. Thus, accuracy of the tracking by the reproducing head requires improvement.
U.S. Pat. No. 4,720,753 discloses an auto tracking apparatus for solving the above-mentioned problems. A schematic block diagram of the auto tracking apparatus for the above publication is shown in FIG. 1.
This auto tracking apparatus is arranged to divide a tracking period of one field of a frame into a plurality of time domains and to sample and hold the envelope detection output signal of a reproduced high frequency signal of every time domain.
However, for achieving these features, that apparatus has a relatively complex construction; it would be desirable to provide more simplified and improve apparatus in its construction.